Abaixo está uma instrução que descreve uma tarefa de geração de SQL, combinada com uma entrada que fornece mais contexto sobre os esquemas de tabela disponíveis. Escreva o código SQL que responda adequadamente à solicitação
 ###Instrução: Qual era a nacionalidade do nadador na semifinal com um tempo de 29.51?
 ###Tabelas: CREATE TABLE siena_college_research_institute_survey (siena_college_research_institute_survey_id AUTO_INCREMENT PRIMARY KEY, Seq. VARCHAR, Name VARCHAR, Background INT, Party Leadership INT, Communication Ability INT, Relations with Congress INT, Court Appointments INT, Handling of Economy INT, Luck INT, Ability to Compromise INT, Willing to take Risks INT, Executive Appointments INT, Overall Ability INT, Imagination INT, Domestic Accomplishments INT, Integrity INT, Executive Ability INT, Foreign Policy Accomplishments INT, Leadership Ability INT, Intelligence INT, Avoid Crucial Mistakes INT, Expert's View INT, Overall INT) CREATE TABLE women (women_id AUTO_INCREMENT PRIMARY KEY, Event VARCHAR, Date VARCHAR, Round VARCHAR, Name VARCHAR, Nationality VARCHAR, Time VARCHAR, Record VARCHAR) CREATE TABLE 1988_boys'_team (1988_boys'_team_id AUTO_INCREMENT PRIMARY KEY, Player VARCHAR, Height VARCHAR, School VARCHAR, Hometown VARCHAR, College VARCHAR, NBA Draft VARCHAR) CREATE TABLE handicap_results_top_10 (handicap_results_top_10_id AUTO_INCREMENT PRIMARY KEY, Position INT, Sail number VARCHAR, Yacht VARCHAR, State/country VARCHAR, Yacht type VARCHAR, LOA (Metres) INT, Skipper VARCHAR, Corrected time d:hh:mm:ss VARCHAR) CREATE TABLE unreleased_songs (unreleased_songs_id AUTO_INCREMENT PRIMARY KEY, Title VARCHAR, Author(s) VARCHAR, Recorded VARCHAR, Location(s) VARCHAR, Time VARCHAR)  
SELECT Nationality FROM women WHERE Round = semifinal AND Time = 29.51